Technical Abstract:
Methodology was developed to record electroencephalograms (EEGs) from chickens using skin surface contact electrodes and telemetry transmitter and receiving units prior to and immediately after electrical stunning. Optimal location of the three electrodes was determined using scaleless ¿featherless¿ chickens. Broilers required plucking of feathers on the neck caudal to the comb (~2 x 3 cm) under mild anesthesia the day prior to recording EEGs. The telemetry transmitter was protected from the stunning voltage with a custom-built circuit designed to reduce high amplitude AC and DC voltages to less than 0.8 V. This configuration permitted recording of EEG signals prior to and within 3.5 s after termination of the applied stunning current. EEGs were recorded during two different electrical stunning protocols with the current applied to a standing chicken (wattle + and vent -). The first stun protocol was at 8 mA, 12 V (500 Hz) pulse DC for 11 s immediately followed by 12 V (60 Hz) AC for 4 s. The broilers were given several minutes to recover and then stunned again using the second stun protocol set at 103 mA (60 Hz AC) for 4 s, which was sufficient to induce cardiac arrest. The EEG recordings of the second stun protocol were evaluated to determine wave characteristics and the duration of poststun brain activity. The poststun EEG recordings depicted a brief period of high amplitude spikes, which progressively diminished in amplitude with time. This high amplitude polyspike wave form has been assumed to be analogous to the insensibility period that occurs during epileptic seizures in humans. This poststun data, in both wave form and duration of brain activity (39 s), appears similar to that described in the literature for chickens (32 s). Use of the cutaneous-telemetry system to record brain EEG activity in chickens following electrical stunning may provide the opportunity to quantitatively optimize stunning voltage, current, and frequency. Optimal stun parameters should minimize the time to death, and diminish skeletal muscle contraction and the carcass defects associated with electrical stunning.